Here’s a pop quiz: how many people diagnosed with essential tremor (ET) actually have something different? What’s your guess? Is it:

a) 11%
b) 37%
c) 50%
d) 66%

If you said either b or c, you are correct—depending on which of two studies is your source.

There are two pertinent studies that took the trouble to find out how often doctors make an incorrect diagnosis. The first (Shrag, et al.) was published in 2000. As their criteria for distinguishing ET from other types of tremor, the authors used a 1994 description of observable characteristics developed by Bain, et al. The authors then randomly selected 50 patients who were diagnosed with ET by any neurologist at their institution and determined how many of them matched the Bain criteria. Of the 50 individuals, 25 of them – or 50% – actually had a different tremor-causing condition than ET! In other words, half of the patients had been misdiagnosed.

The second study (Jain, et al.) came out six years later in 2006. Its title was provocative: “Common Misdiagnosis of a Common Neurological Disorder: How Are We Misdiagnosing Essential Tremor?” That’s a good question. As their criteria for distinguishing ET from other conditions, they used the 1998 Consensus Statement of the Movement Disorder Society on Tremor. The authors re-evaluated 71 persons who had been diagnosed with ET. Based on the consensus statement definitions, the authors determined that 27 of them – or 37% – had been wrongly diagnosed.

If the participants in these studies didn’t have ET, what did they have? The list includes Parkinson’s disease, dystonia, neuropathic tremor, unilateral leg tremor, drug-induced tremor, and sudden onset following head trauma.

Implications of misdiagnosis

Being diagnosed with ET when you don’t have it is called “false ET.” It’s hardly good news, especially if what you really have is Parkinson’s disease. There are layers of implications involved in receiving an incorrect diagnosis. As the Jain paper points out, being misdiagnosed can lead to numerous treatment errors. In turn, this can result in months or years of frustration, needless side effects, and discouragement. Some patients start to feel a little crazy, like “what’s wrong with me that this drug that works for others has no effect on my tremors?”

It’s hard to think of anywhere from a third to a half of people who experience tremors being wrongly diagnosed and then struggling along from one treatment to another. Even among those who, in fact, do have ET, the standard medications (beta-blockers, anticonvulsants, and various combinations) are not equally effective for everyone.

Additional clues help identify the tremor type

To return to the question raised in the Jain title, how is it possible that even experienced neurologists make a diagnostic mistake regarding ET? One answer may be missing an unusual clue like an isolated thumb tremor or a non-rhythmic tremor. Another may be overlooking or considering other, more rare types or causes of tremor. A third may be failing to screen for drug or alcohol abuse, or exposure to toxins.

As the Shrag paper sums it up, “The diagnosis of ET is overused even among experienced neurologists, and other types of tremor should be considered in atypical patients before making this diagnosis.” I would add, as with any diagnosis of a serious medical problem, when diagnosed with ET it may be worthwhile to get a second opinion, if possible.